Hydraulic transmission



March 1944- 5. A. WAHLMARK HYDRAULIC TRAN5IMSSTON Filed Sept.

12, 1939 5 SheetsSheet'l mew l I INVENTOR Y Gan/Zara. il QfzZ/rzar A) 68,; @w I; ATTORNEY.

March 14, 1944. G A] WAHLMAR 2,344,335

HYDRAULIC TRANSMISSION Filed Sept. 12, 1939 s AheetS- -Sheet 2 44 mag 373535 I NVENTOR.

GzuzzzarQ ll cz/zZzrzar/g I 3 Yam March 14, 1944. e; A. 'WAHLMARK HYDRAULIC (TRANSMISSION 5 Sheets-Sheet 4 Filed Sept. 12, 1939 W $533M NMM/ WAR, BQm, m QM, RNmM W W QR k I] H iv v l mm x flaw Q Qww WW J \NN, QWMI Q%\ m Q A 6 AW mwN March 14,1944. G. A. WAHLMARK 2,344,335

HYDRAULIC TRANSMISSION Filed Sept. 12, 1939 5 Sheets-Sheet 5 1N VEN TOR. Gumar CZ. ZZ/a/zlmarb,

44 A ORNEY.

Patented Mar. 14, 1944 UNITED STATES PATENT OFFICE q HYDRAULIC TRANSMISSION Gunnar A. Wahlmark, Rockford, m.

Application September 12, 1939,,Serial No. 294,470

' (c1 co -53) 18 claim.

More particularly, the invention relates to transmissions having a constant speed input shaft and an adjustable speed output shaft, it being the general obiect of the invention to provide a new and important transmission of this type.

Another object is to provide a hydraulic or fluid transmission embodying a variable displacement fluid pump and a variable displacement fluid motor, together with means for controlling the displacement of the pump and the displacement of the motor to obtain any one of a plurality of predetermined output or driven shaft speeds.

In adapting fluid transmissions for use in actuating movable supports in machine tools, as well as for other applications, it is frequently desirable tov have available arelatively large number of driven shaft speeds which may be obtained automatically or at the will of the operator by actuation of one or more control elements, the various speeds, however, being preselected or preadjusted. In a fluid transmission embodying a pump and a motor, the changes in speed may be obtained by changing the strokes of the pistons of one or both such devices. The present invention has for an object the provision of a new and improved control mechanism for adjusting the stroke of a fluid pump or motor to preselected lengths.

Another object is to'provide a control for such a fluid transmission embodying a plurality of independently adjustable stop elements and mechanism connected to the wobble plates of the 4 pump and motor having means engageable selectively with said adjustable stop elements.

Another object is to provide a new and improved control mechanism for fluid motors embodying a control element movable to adjust the motor speed and a plurality of independently adjustable and independently operable stop members for determining the position of the control element.

It is another object of the invention to provide a new and improved fluid transmission enrbodying a fluid pump, a fluid motor, and speed reduction gearing, together with fluid operated devices for selecting the speed at which the output shaft of the transmission is driven.

It is a further object of the invention to provide a new and improved fluidtransmission embodying a reversible output fluid pump, a fluid motor arranged to receive the output of the pump and be driven thereby, a make-up pump, and a eluding a reversing valve operable automatically to direct make-up fluid to the return passage from the motor to the pump.

Other objects will become readily apparent from the following detailed description taken in connection with the accompanying drawings, wherein:

Fig. 1 is an end elevational view of a preferred form of the invention looking at the right hand end of Fig. 2.

Fig. 2 is a front elevational view thereof looking from the left in Fig. 1.

Fig. 3 is top plan view. v

Fig, 4 is a longitudinal central section approximately along theline 4-4 ofFig. 1.

Fig. 4a is a fragmentary view along the line 4a-4a of Fig. 4.

Fig. 4b is a fragmentary view along the line 4b-4b of Fig. 4.

Figs. 4c, 4d, 4e and 4! are fragmentarysections approximately along line 40-40, lit-4d, 4e-4e and 41-4f, respectively, of Fig. 4.

Fig. 5 is an enlarged fragmentary vertical section approximately along the line 5-5 of Fig. 3. a

Fig. 6 is a fragmentary .plan

sectional view along the line 6-4 of Fig. 4. A

Fig. 7 is a vertical section approximatelylalong the line 1-1 of Fig. 3.; p Fig. 8 is a section along line ofil'ig; I.

Fig. 9 is a circuitdiagrampf aportion of the. I

control mechanism, showing a valve in transverse section. I

Fig. 10 is a circuit diagram.

Fig. 11 is a fragmentary vertical section in the same plane as Fig. 4 but illustrating a modified form of the invention. 7

Fig. 12 is a similar fragmentary view illustrating still another form of the invention.

While there is illustrated in the drawings and hereinafter described in detail a preferred form of the invention, together with two modifications thereof, it is to be understood that the invention is not limited to the particular forms and arrangements shown, it being contemplated that various changes may be made by those skilled in the art without departing from the spirit and scope of the appended claims.

As illustrated in the drawings and with particular reference to Figs, 1 to 10, the invention comprises a somewhat rectangular casing 20 provided with feet or attaching lugs 2| at'the bottom thereof, and a detachable cover 22 on the top thereof, To the left hand end of the casing 20 as viewed in Figs. 2 and 3, is secured an adapthydraulic circuit connecting said devices and iner 2: by which is mounted a suitable electric driva the transmission.

ing motor 24. At the other end of the casing is supported a housing 25 of a speed change mechanism 26 (Fig. Secured in an upright position on the front wall of the casing 20 is a multiplepiston variable displacement motor 3|.

The pump has a shaft 32 rotatably mounted in bearings 33, and 35. It will be assumed, for purposes of this description, that the motor 24 drives the shaft in a clockwise direction, as viewed from the left in Figs. 2 to 4. A plurality of cylinders 36 are arranged annularly about the shaft 32 in a cylinder block 31 and have pistons 38 therein which are operable by means of a wobble plate device 39. The wobble plate device has an outer annular member 40 engaging the adjacent spherically surfaced ends of the pistons, and an inner annular member 4| pivotally mounted on the shaft 32 by means of a diametrically extending pin 42, a plurality of balls 43 being positioned betweenraces formed on the members 40 and 4| to form a rotary connection therebetween. The cylinder block 31 is supported in an inwardly extending tubular portion 44 of the adapter 23.

The means for adjusting the wobble plate device 39 includes a member 50 slidable longitudinally in a slot 5| in the shaft 32, the member 50 having an outwardly extending arm 52 which engages in a recess 53 in the annular member 4|. At its right hand end, the member 50 has a plurality of outwardly extending teeth 54 which are interengaged with corresponding grooves in an inner ball race 550i a bearing 68. The outer race 51 of this bearing is formed integrally with an annular member 58 slidably mounted in abore 59 in the cylinder block 31. A control lever 60 has its lower end positioned in a socket 6| in the member 58 and its upper end positioned in a socket 62 in a,piston 63 slidably mounted in a cylinder 64 (Figs. 4 and 4f). Cylinder 64 is formed in a block or housing member I53 which is suitably bolted to the top of the adapter portion 44. An

intermediate spherically surfaced portion 65 of the lever 60 is fulcrumed in a bushing 66 secured in the cylinder block 31. Thus, movement of the piston 63 in its cylinder 64 serves to swing the lever 60 and thereby effect longitudinal movement of the member 50 to increase or decrease the displacement of the pump 30, or to reverse the direction of the flow of fluid therethrough.

The flow of fluid to and from the head ends 36' of the cylinders 36 is controlled by means including a wheel-like valve member 10 which is mounted on an eccentric pin portion 1| (Figs. 4 and 4a) of the shaft 32 by means of a ball bearing 12. This particular valve mechanism is disclosed and claimed in my copending application Serial No. 143,069, filed -May 17, 1937, now Patent No.

r 2,190,812, dated February 20, 1940. Briefly, the

valve member 10 is positioned in a cylindrical valve chamber 13 formed between an end face 14 of the cylinder block 31, an adjacent end face of a housing member 16, and a ring 11 secured between said end faces. As illustrated in Fig. '4, the parts 44, 31, 11 and 16 are secured together by means of a plurality of bolts 18. The head ends 36' of the cylinders are formed by means of cup-shaped inserts 19 provided each with 9. cylinder port shaped like the ports I40 shown in Fig. 40. During the operation of the pump and the valve 10, the cylinder ports 80 are connected alternately with the outer portion of the chamber 13 and the inner portion thereof. The outer portion of the chamber communicates with an outlet passage 8| which extends through the housing member 16 and into communication with the outer portion of a similar cylindrical valve chamber 82 for the motor 3|. chamber 13 is connected to the inner portion of the motor valve chamber 82 by ports 83, 85 and 86. Make-up fluid is supplie manner hereinafter more f an auxiliary gear type pump 81 (Figs. 4 and 10).

The motor 3| is similar in construction to the pump 30 and has a shaft 92 rotatably mounted in bearings 83, 94 and 95. Rotation of shaft 82 in a clockwise direction, as viewed in Fig. 1, will hereinafter be considered as forward operation of the motor 3|. A plurality of cylinders 96 are arranged annularly about the shaft 92 in a cylinder member I00 engaging the adjacent spherically,

surfaced ends of the pistons, and an inner annular member |0| pivotally mounted on the shaft 32 by means of a diametrically extending pin I02, a plurality of balls I03 being positioned between races formed on the members I00 and IM to form a rotary connection therebetween. The cylinder block 91 is supported in part by a tubular member I04 supported at its right hand end (Fig. 4) in a bore in an end wall 20 of the casing 23.

The means for adjusting the wobble plate device 99 includes a member 0 slidable longitudinally in a slot I I I in the shaft 92, the member III having an outwardly extending arm 2 which engages in a recess 3 in the annular member IOI. At its left hand end (Fig. 4), the member 0 has a plurality of outwardly extending teeth 4 which are interengaged with corresponding grooves in an inner ball race I 5 of a bearing III. The outer race II 1 of this hearing is formed integrally with an annular member II 8 slidably mounted in a bore 9 in the cylinder block 91.

end positioned in an opening in a piston I22 slid-- ably mounted in a cylinder I23, the lever being i I pivotally connected to the piston I22 by a pin- I24. The cylinder I23 is formed in a housing member I53 suitably secured to the right hand end 01' the housing member I 53. An intermediate spherically surfaced portion I25 01 the lever I 28 is fulcrumed in a bushing I26 secured to the cylinder block 91. Thus, movement of the piston I22 in its cylinder I23 serves to swing the lever I20 and thereby effect longitudinal movement of the member 0 to increase or decrease the displacement of the motor 3|.

The flow of fluid to and from the head ends I. of the cylinders 96 is controlled by means including a wheel-like valve member I30 which is mounted on an eccentric pin portion I3I (Figs. 4 and 4b) of the shaft 92 by means of a ball bearing I32. The valve member I30 is positioned in the cylindrical valve chamber 82 which is formed between an end face I34 of the cylinder block 91, an adjacent end face I35 of the housing member 16 and a ring I31 secured between said end faces. As illustrated in' Fig. 4, the parts I04, 91, I31 and 16 are secured together by means of a plurality of bolts I38. The head The inner portion of the to the circuit, in a y described, from operation of the motor-audits valves I30, the

cylinder ports It! .areconneoted alternately with the uter o m tjm t o ib Y the innenor,outletportiozi'thereof: Inthe :i'orm, illustrat'edi flj'ligsfilito' 10. the

speedt ,the ,--mo,tor I shaft ,92 adjusted by chansms the angular. osi ions. ot the wobble thefchaznber 82 and plates and 996: the'phmp alidinbtor, raspy} tively. JI 'he changes in angula positions or these; wobble-she h eati qmnnsh a ta ously bx; mecha ismga po o f n t "wh hfihas hereinbefoife; heel; desoribedfandl the-remainder w w l now be d i ir efr isp fi ticularly ta-rigsisi and 4f,'the pistontsto which the upper end of}- the pump a justin lever it is connected has -;rack teeth ,I 50 which mesh "with .arpinionmlil @rotatahl'y mouht o 2on1 a shaft I 52 wh h suppor ed fl ed sh n I bolted toithfi housm we 53 ;Y h e n s -64 for-the piston 63 Iio h th s sin member as is also an adj ace'nt and parallel cylinder I-54- I in t which a; piston I55 QreCipIQcates. PlstOnI-ISS hasraclr teeth I'5Iifalso ineshing'with 1 th pinion II so th'at as thepistomfl moves in one direction thepistonjl5i movesu the op- 'p'osite ,,direction,g 'r e right hand v ends r the cylinders; cr ne lsl r'i eiq are interconnected by means of arecess li'l I housin membe I 5. 1 {C ind (84.- 1 5 fp' ov d .:with aport I58 thecas'ing I 6 2., 3 and cylinder 1541 is provided ,wi ,h', a {similar port/I 59;' Fluid I 1 I may be supplied ,1; eitheriot jv saidifyiinders by mana es i vertical shore reverseposition. "A portfi lfl in the housing 1 operating arm isin the ,f stop. position, asishown 1th. the inder ports I .158 and 159,-. respeotively,..as'shown in Figs. 4d i .and;4e.-.;Whnthe handle. no ismovedto the ".forwardl position, fluidlisfs ll p ied from the I I radial port IBS ofQtheyalVe member through the .cylinder; port I59 to the cylinder j I lili'whereupon the piston J95 isgmoved towardthe right (Fig. 4).'-,This causes the piston '63, through the in- I tervening rack andpinion connections, to move towardthe left, therehy 'swingingthe wobble plate 39 ina olockwise direction'fabout thepivot I pin l2. Ii the ,operatingfhandle I10 is moved seesaw I 3 ends fl' o t the cylinders are, iormed by means oticup-shaped I 39 providedegach with a valve member I92 is also provided with side wall slots I69 and- I89 which connect respectively with longitudinal .exhalustports lfll" and I69" to relieve thepressure in theends ot the cylinders 64 and I54 when not connected to the il-uid supply.= Ports I98" and I69 discharge at the igw'eroend ot the valve member and into the eass-z; W .I II v inordrtoadiust the wobble plate, or. the motor simultaneously with the wobble. plate" 8'! of-the pun'rp, movement-is imparted to the piston I22 by means of-a cylindrical member I (Figs'hiandm) slidably mounted ina-bore I" in the housing J53; which bore is aligned with the cylinder I23. The member I19 atits left hand T end projects into the recess 451 ,50 as! to I he engageableby one or both 01 the pistonsli,

I55. At its right hand end, the member I15 carries an adjustable screw device I11; the head I18 of which is. adapted: to abut the adjacent and oi' the piston I22. This, movement ot either of the pistons 63; 155 toward (theright trorn the I zero stroke positionshown in Figs. 4 Ian d 10,"will j'rhe ert hand ena or a I the cy inde ar vi rmfi. i vfll ba 'ngi "i zsuitablyhsecuredhto .the lett hand end of the cause movement of the cylindricalmemberfI-IS and the piston I22 toward the rightQthiihhua -ing acounterclockwisevmovement o! the .gwol'lblo plate 99 onits pin I92 from the maidmumfstro'il're' position shown to a shorter stroke position.v

which shorter stroke-position is determined by a control mechanism hereinafter more fully described. I Itwill be evident that the wobble plate device' 99 willbe moved in a counterclockwise direction from" its full stroke position regardless ptwhether pistonwtifunctions to operate the wobble plate 39 or whether the piston I55 functions to operatethe vwobble plate 39 ;Thus, the

stroke or themotor is adjusted frommaximum toward minimum tor. both forwai'rd and reverse rotation of the motor shalt. The wobble plates are normally held in thepositionsiIlustratedin Fig.- '4'-by fluid under pressure-which is constantly admitted. w the right .hand'end I23" of the ori- .}lnder-|23.-- I I :Q'Inthe form illustratedin Fi s. 1 to the inventionis shown as embodying a speed; change mechanism 25 (Fig, 5) in which the drive" shaft is the shaft 92 of the motor BI .and the driven shaft is the output shaft"!!! of the transmission. The speed change mechanism comprisesanlannularadapter I90 (Figs. 2, 3 8116.5) securedtolthe casing '20- by means of aplura-lity of bolts I9I,

an annular housing member I92 secured to the [adapter I90 by means of aplurality of bolts I93 1 and a cover member I94, secured to the housin I92 b'y means of a piuralityof bolts I95. ,I'he

I output shaft 28 l is rotatably. mounted on the cover member I94 bymeans of aball bearing I96, and

w in Figs. 2 to I68 jandilfifare hoth I I out of; communication at its inner I end has a radially extending flange *I9'Lf A collar I98 issecuredto said flange by t0 the reyel'sefposltiomthe radialportIBIi of the valvemember supplies fluidto thecylinder I ort, I58 t move'gt piston ,sa toward the right,

: thus-pivoting the wobble plate 39 in" a contour zciockwlse dir'ectionon thepivot pin 42. The

means of a plurality ofbolts I99, and to support the inner end of the shaft-28ahall bearing'flmu ispositioned intermediate the collar I98 and the motorshaft92r ,I h v In the form illustrated herein, the speed change mechanism 26 I consists .of planetary gearing. Thus; a sun gearor pinion- ZI'II (Fig f5) is secured-to the motor shaft 92-by1meansota'key 232 and meshes withv a-plurality of planet gears 293 (preferably three in number) which are rotatably mounted .on a planet carrier formed by the flange-I81 of the shaft 28 and the collar I98, by'meansofrollerbearings 204 and s'haftshZIlS.

-'A ring gear 20$,mesheswith the planet ears WI 203. A clutchplate 201 is formedlint egrally with 76 the ring gear and with a tubular'mem'b'or 208 which surrounds a portion of the shaft 28. The ring gear is rotatably mounted on the housing I92 by means of a ball bearing 208 interposed between the tubular member 208 and a bushing so as to hold the ring gear stationary, the output shaft 28 is rotated at a reduced speed com-- pared with the motor shaft-82.

The operation of the speed change mechanism just described is accomplished by the piston 2II operable in the cylinder 212 by supplying fluid under pressure to one end or the other of the cylinder. As illustrated in Fig. 5. a port 220 communicates with the left hand and of the cylinder H2 and a port 22I communicates with the right hand end of the cylinder. The supply and control of fluid to these ports will be described hereinafter in connection with the hydraulic circuit illustrated in Fig. 10.

The speed of the motor shaft 92 may be varied from zero (which occurs with the parts in the positions shown in Fig. 4 wherein the pump stroke is zero and the motor stroke is at'maximum) to a maximum speed when the pump stroke is at a maximum and the motor stroke is at a minimum.v

Intermediate speeds of the motor shaft are obtained by means of a control mechanism now to The gearing just described including shaft 230, pinion 23I, rack teeth 232, pinion 236, and rack teeth 231 form a connecting means between the control element 238 and the control piston I22 240, to preselect a speed of the motor shaft 82. When in such a position, as illustrated in Fig. '1', the flange 250 of the control element 238 engages v the abutment 248 on the piston 246 to determine the position necessary to obtain the preselected motor speed. Preferably, the control element 238 is urged upwardly continuously by fluid under pressure operable on a piston 210 which is reciprocable in a cylinder 2' positioned below the control element 238 in the bore 239. This cylinder is in the form of a cup-shaped bushing secured in position by means of a pin 212. Fluid is supplied to the lower end of the cylinder 2" by means including a port 213 and a connecting supply port 214.

The pressure supplied to the reversing pistons 63, I55 (Fig. 4) may be approximately 1,000 pounds per square inch.

shaft 23I in a clockwise direction, as viewed in The force exerted by I the reversing pistons is effective to rotate the 2I0, the inner and outer races of the bearing 5 so that the control piston I22 will be shifted to being clamped to the member 208 and the bushdifferent positions corresponding to or having a ing 2I0, respectively, by means of screw-threaded fixed relation with the different positions of the nut devices 209 and 208". The bushing M0 is control element 238.

slidable longitudinally of the housing and has a The means for preselecting different positions 7. piston portion 2 reciprocable in a cylinder 2l2 of the control element 238 includes a plurality of (in the housing) for the purpose of shifting the screw devices 240, herein six in number. These clutch plate 201 from one to the other of two screw devices are threaded through an annular engaged positions. When shifted toward the left member 24I which is secured to the upper end (Fig. 5) a clutch surface on the clutch plate of the cylindrical housing 233 by means of a pluformed by a plurality of annular ribs 2I3 engages rality of screw devices 242. The screw devices a clutch face on the planet carrier formed by 240 are threaded at their lower ends 240' and corresponding annular ribs 2 on a clutch plate engage in threaded bores 243 in the member 24!. 2|! which is secured to the radially extending The upper ends of the screw devices 240 are flange I81 of the shaft 28. When the clutch squared as at 244 to receive a suitable tool for plate is moved toward the right, a clutch suradjusting purposes. Aligned with each screwI face formed by a plurality of annular ribs 2I6 240 is a cylinder 245 in the housing 233. A pison the plate 201 engages a corresponding clutch ton 246 is positioned in eachcylinder 245. The surface formed by annular ribs 2 on an annular pistons 246 have side wall recesses leaving shoulstationary clutch member 2I8 bolted to the housders 241 and 248 at the upper and lower ends ing I92 by means of a plurality of screws 2I9. 25 thereof (Fig. 7). An annular flange 250 formed When the clutch plate 201 is shifted toward the integrally with the control element 238projects left into engagement with the planet carrier, the into the recesses in the pistons and is movable gears become locked and the output shaft 28 vertically therein.

rotates in unison with the motor shaft 82. When The pistons 246 are effective, when in their upthe clutch plate 201 is shifted toward the right 30 per positions abutting the corresponding screws be described.

The control mechanism 21 (Figs; 1 to 3 and 'l to 10) is operative to determine a plurality of the annular flange 250 therein engages the'abutmerit surface 248 on that piston 246 which is then-J 3 efiective to determine the speed of the output preselected positions of the control piston I22 (Figs. 4 and 10) and includes a shaft 230 extending transversely of the casing 20 (see Figs. 1 and 3) and having a pinion 23I thereon meshing with rack teeth 232 formed on the piston I22. The shaft 230 projects outwardly from the casing 20 and Tnto a hollow somewhat cylindrical housing 233 (Figs. 7 and 8) which is secured in position to one side of the casing 20 by means or a plurality of bolts :34. At its outer end the shaft 230 is supported in said housing by means of a ball bearing 235. Secured to the shaft 230 is a pinion 238 (Figs. 1, 3, 7 and 8) which meshes with rack teeth 231-formed on a cylindrical plunger 238 which is slidable vertically in a bore 238 positioned centrally of the housing 233. The cylindrical plunger 230 is, functionally, a control element which is movable to. any one of a plurality of predetermined positions for the purpose of changing the speed of the motor shaft 82.

shaft. Fluid from the samesupply source of approximately 1,000 pounds per square inch is fed to the port 214 and, therefore, is applied to the piston 210 as well as to the preselected piston 246 to hold the latter upwardly in engagement with the corresponding screw 240. The piston 218, which is ofsomewhat smaller diameter than the reversing pistons 63, I55, is provided to reduce the effect of the reversing pistons in causing downward movement of the control element 280, thereby insuring the effectiveness of the piston 206. Each of the pistons 248 is of such cross sectional area that with the aid of the piston 210 it is able to overcome any tendency of the reversing pistons 63 and I55 to shift the control element 230 downwardly as viewed in Fig. 10.

The selection of the different motor speeds is herein accomplished by means of a cylindrical valve 215 (Figs. 7 and 10) mounted in the'lower end of the bore 289. This valve is provided with a stem 216 projecting downwardly from the houslng 233 and has six operative positions, one for each of the speed selecting pistons 246. A detent device 211 ispreferably provided for releasably holding the valve in its different positions. The valve 215 has an annular groove 218 positioned to receive fluid from the supply port 214 and also has a diagonally extending port 219 which communicates at one end with the groove 218 and at its other end with the outer surface of the valve, as shown most clearly in Fig. 7. When in the position illustrated, the port 219 communicates with a short horizontal port 289 which in turn communicates with a vertical port 28| discharging at its upper end into the lower end of 9. cylinder 245. As illustrated diagrammatically in Fig. 9, there is a set of ports 289, 28| for each cylinder 245. Thus, by rotating the valve 215, the port 219 may be selectively connected with any one of the plurality of ports 289 with the result that fluid is supplied to the corresponding cylinder 245 to move the piston 246 therein upwardly into engagement with the lower end of the corresponding screw 249. To permit discharge of fluid from the cylinders 245 when not connected to the diagonal port 219, the valve 215, outwardly of port 219, is formed with a groove 282 (Figs. '1, 9 and 10) interrupted by a segmental portion 283 (Fig. 9) through which port 219 opens. This groove is at all times open to all but one of. the ports 289 and is also in constant communication with a port 284 in the casing 233 leading to the tank.

. Means is preferably provided forindicatingthe speeds for which the screws 249 have been ad- Justed. illustrated herein (Figs. 2 and '7) this means includes a plurality of indicating rings 285,- one for each or the screws 249. These rings have internal gear teeth 286 thereon. Each screw 248 1 is provided with a pinion 281 secured thereto by a key 288, the pinion of each screw 248 meshing with a different ring 285. The upper end oi the control mechanism isenclosed by means 0! a cap 299 secured to the member 24|-by means of a screw device 298 which extends through the cap 239 and into engagement with a plug 29l threaded into the upper end of a bore 292 in the member 24!. i As shown in Fig. I, the control element 238 has its, upper end projecting into the bore 292 for guide purposes and a relief port 238 is provided in the element 238v to drain leakage fluid from the bore 292. The cap 289 has a somewhat rectangular opening 293 in one side thereof through which the adjacent portions of the indicating rings 285 are visible. These'rings may be provided with suitable indicia. For example, with a speed change mechanism 26 (Fig. 5) having a 4:1 ratio, the rings may be marked in steps from 2400/6300 to /25 R. P; M. for theoutput shaft 28, the higher-range oi speeds (2409/109 R. P. M.) being obtained when the speed change mechanism is in direct drive and the lower range speeds (600/25 R. P. M.) when the speed change mechanism provides a 4:1 speed reduction.

The fluid circuits for the transmission, to-

gether with certain portions 01 the control, are

illustrated most clearly in Fig. 10. A fluid supply is contained in a reservoir 389, which reservoir in Fig. 4 is shown in the lower portion of the casing29. Fluid from the reservoir 399 is drawn through a conduit 39!, a strainer 382 and a conduit 393 to the gear type pump 81, whence it is discharged into a conduit 394 (Figs. 6 and 19) at a pressure of approximately pounds per square inch. Fluid supplied to the conduit 394 passes to connecting ports 394' and 394". Excess fluid is by-passed through an adjustable relief valve 395 (which is backed by a. coiled spring 395') to a conduit 396 which has nozzle connections 381 and 398 arranged to direct the by-passedfluid on to the wobble plate devices 39 and 99 of the pump 39 and motor 3|, respectively. Since the fluid used is preferably a good quality of lubricating oil, the by-passed oil is thereby used for lubricating parts of the mechanism. The conduit 394" communicates with the casing of a reversing valve designated-generally 3|8. The casing of this valve has a cylindrical bore 3| in which a cylindrical valve member 3|2 is reciprocable. Conduit 394" connects with an annular groove 3|3 in the valve casing which is spaced from one end of the valve bore 3. A corresponding groove 3|4 is spaced from the opposite end of the valve bore. A third annular groove 3| 5 is located substantially centrallyof the valve bore. One end of the valve bore 3 is connected by means of a conduit 3|6 to one of the ports 86 in the housing member 16. The other end of the valve bore 3 is connected by means of a conduit 3" to the port 8| in the housing member 86. The conduits 3|6and-3l1 are used alternatively, depending upon the di rection oi'fluid flow through the pump 39, to

supply make-up fluid to the pump and motor cylinders and the fluid passages therebetween. Since it is desirable to supply the make-up fluid to the return passage from the motor 3| to the pump 39, the reversing valve 3|8 is provided so that the flow of make-up fluid may be changed from conduit'3l6 to conduit 3|1 or vice versa when the wobble plate 39 of the pump is shifted through its zero stroke position. At the same time the valve 3|9 functions to'control the flow of high pressure fluid from the pump-motor cir cuit to portions of the other circuits requiring high pressure fluid for control purposes.

The valve member 3|2 has spaced annular grooves 329 and 32| (Figs. (Land 10). Longitudinally extending ports 322 in the valve member establish communication between the annular groove 328 and the lower end of the valve member (Fig. 10) and longitudinally extending ports 323 establish communication between the annular groove 32l and the upper end of the valve. These ports function to pass high pressure fluid .to the groove 3|5 in the valvecasing, the ports 322 functioning in this manner when the valve member is in its raised position as shown and the ports 323 functioning in this manner when the valve member is in its lowered position at the other end of the valve bore 3| A port 325 connects with the groove 3|5 and communicates at its other end with a high pressure reliei valve 326 which is backed by a coiled spring 326' (Figs. 6 and 10). A conduit 321 connects with the conduit 325 for the purpose of supplyinghigh pressure fluid to the passage |63 leading to the reversing valve I68 (Figs. 4 and 10). A conduit 328 connects with the conduit 321 to supply high pressure fluid to the ports 214 and 213 (Fig. '7)

1n the housing 233 of the control mechanism.

Low pressure fluid from the pump 81 is also utilized in the operation oi'the shiftable clutch plate in the speed change mechanism 25. As shown in Fig. 10, a conduit 338 connects with the annular groove 313 of the valve 3|8 and communicates with a valve 33| (Figs. 4, 6 and'lO). This valve is operable in one position to direct fluid into a conduit 332 which communicates with the port 229 (Fig. 5), or through a conduit to which the conduit 333 is connected. A diametrically opposite casing port 34I is adapted for connection to the conduit 332 so that when the valve member 331 is rotated in a counterclockwise direction (Fig. 6) to connect the port 340 to the port 34I, the clutch plate of the speed change mechanism is shifted to its direct or high speed position. The valve member 331 is cut away at 331 to permit fluid to exhaust from the inactive end of the cylinder m. As shown in Fig. 6, fluid returning through the port 34I passes downwardly in the bore 335 and into the casing 20 (Fi 4).

The fluid circuits as shown also include a conduit 345 connecting the low side of the high pressure relief valve 326 to the conduit 330. A ball check valve 345, backed by a coiled spring 343', is connected between the annular groove 3I5 and the conduit 304" by conduits 341 and 348 in a manner to prevent flow of the high pressure fluid back into the low pressure conduit 304" although under certain circumstances, such as when starting up the transmission, it permits low pressure fluid from conduit 304" to pass to the groove 315. Low pressure fluid is supplied continuously to the right hand end of cylinder I23 by means of a conduit 349 (Fig. 10) which connects at one end with the low side of the high pressure relief valve 325 and also connects by means of a branch conduit 350 with groove 3 of valve 3I0.

In the invention in the form just described, the stem 213 of the speed selector valve 215'may be operated manually by means of a suitable handle (not shown). When the invention is used in connection with a machine tool, however, means is preferably provided for operating the valve 215' automaticalLv in accordance" with the functioning of the machine. As illustrated in Fig. 10, the valve stem 218 has a beveled gear 360 thereon meshing with a second beveled gear 36I secured to a shaft 362. Intermeshing bevel gears 383 and 364 connect shaft 362 with a shaft 365, one end of which is secured to a tool turret 366 of the type generally provided in machines such The tool turret of such a maas turretJathes. chineds generally indexed automatically during the operation of the machine, the connections just described providing-for the indexing of the valve 215 simultaneously with the indexing of the tool turret. In this way, a difierent speed of operation of a machine part (driven from the output shaft 28) may be obtained for each tool.

for oil cooling purposes. With a speed change mechanism 28 as illustrated in Figs. 1 to 3 and 5, a handle 315 thereon is moved to one of its two operative positions to condition the speed change mechanism in accordance with the desires of the operator. As shown in Figs. 3 to 5 and 10, the speed change mechanism is in direct drive and the handle 31-5 is in the direct drive position. The handle I10 of the reversing valve I60 is in its stop position with the result that the wobble plate 39 is in its zero stroke position and the wobble plate 99 is at maximum stroke. Under these circumstances, make-up fluid is supplied by the pump 81 but there is no discharge of fluid by the pump 30, excess make-up fluid being returned to the reservoir 300 over the low pressure relief valve 305. In order to provide for operation of the pistons 53 and I55, however, make-up fluid may pass from the conduit 304', through conduit 348, check valve 345, conduit 341, annular groove 3I5, conduits 325 and 321, and ports I63 and I54 to the reversing valve I60,

I so that movement of the reversing valve handle I10, for example, to the forward position permits fluid to flow to the cylinder L54 to 'move' the piston I55 (Fig. 4) toward the right. The movement of the piston under these conditions will be determined by the control mechanism 21 and, more particularly, by the portion of the control mechanism then eflective as determined by the valve 215. With the valve 215 positioned as shown in Figs. 7 and 10, the movement of the piston I55 (Fig. 4) will be stopped when the flange 250 (Fig. '7) engages the abutment 243. The screw 240 shown in Figs. 7 and 10 is adjusted to a stop position, hence there will be no movement and no tilting of the wobble plate 39. High pressure control conduit 328 leading to the control mechanism 21 is initially supplied with fluid from the make-up pump through the conduit 321. Upon adjustment of the wobble plate 33 so as to eifect operation of the pump 30, however, fluid under high pressure is supplied to the control conduits 321 and 328 and thereby to the reversing valve I80 and the control mechanism 21.

With the reversing valve I in its forward position, the valve 3I2 (Figs. 6 and 10) takes the position illustrated therein due to the action of the high pressure fluid acting on the lower (Fig. 10) end of the valve. The high pressure fluid is supplied through the conduit 3I1 from .port 8|, port 8I then serving as a supply port fromthe pump 30 to the motor 3|, and ports 35 serving as return ports. Assuming that the screw 240 of Figs. 7 and 10 is turned down or the valve 215 is turned to render another screw eflective; shift of piston I 55 and control element 238 will take place causing tilting of the pump wobbler plate device 39, rendering the pump efiective to supply high pressure fluid and rotate the driven shaft in a forward direction The transmission will then continue to operate the output shaft 28 in a forward direction. The speed of the output shaft may thereafter be changed either by indexing the valve 215 to one of its other operative positions or by shifting the valve 33I to its low speed position. The output shaft may be stopped or reversed by means of the valve I60. The output shaft may be stopped also by turning valve 215 to the position of Figs. 7.and 10 where the effective screw 240 provides for stop." To change the speed of the output shaft by means of the valve 215, it is merely necessary to move this valve to any one of its other positions. It is not necessary that the valve be moved I which had previously been held in its upper position by pressure fluid, is released. The newly selected piston 246 then determines the speed of the motor shaft 92. If a newly selected speed is faster than the speed previously obtained, the plunger 238 is moved downwardly to its new positiornchiefiy by the high fluid pressure in cylinder I54. If the new motor speed is lower than the previously selected speed, the plunger 238 is moved upwardly from the position shown in Fig. '1 by the action of the newly selected piston 248. Operation of valve 215 results, through the intervening gearing, in a movement 01 the piston I22 (Fig. 4) by the pinion 23I thus causing an adjust- I The rotation of the motor shaft 92 may be reversed by moving the valve ISO to the reverse position. This would require movement of the handle I10 (Fig. 3) in a counterclockwise direction from the position indicated. This movement of the valve I60 causes fluid under high pressure to flow into the cylinder 64 whereupon the piston 83 moves toward the right (Figs. 4 and 10) and shifts the wobble plate 39 in a direction opposite to that caused by the piston I55. This reversal of the wobble plate 39' causes a change in the direction of the fluid through the pump so that the ports 83, 85, 86 conduct fluid under high pressure from the pump to the motor, and passage 8I- serves as a return port. This change in the direction of fluid flow also causes a shift of the valve 3I2 to its lowermost position (Figs. 6 and 10) since the conduit 3I8 which communicates at one end with the port 85 and at the other end with the upper portion of the valve bore 3I I, subjects the upper end of the valve 3I2 to high pressure fluid. The lower end of the valve bore 3I I is then connected to the return passage N by the conduit 3I1, so as to deliver make-up fluid thereto. Unless the valve 215 is actuated simultaneously with the actuation of the reversing 7 The at... m a eflective'io determine the limit of the movement. of the piston I22 toward the right (Fig. 11) by action of the pistons I3 and I55. .As shown, the stop 319 is in a zero speed or stop position.

The operation of this form of the invention is generally the same as that of the form shown in Figs. 1 to 10 so far as the reversing valve I60 is concerned. The speed of the motor is determined by the setting of the stop 319. In order to facilitate adjustment of the speed during operation, the stop 319 is preferably 'rotatably mounted in the bushing 399, and a ball bearing 319' is inserted between the upper end of the stem 319 and the end of the socket in the bushing 299, in which said stem is located.

In the form illustrated in Fig. 12, the speed 5 control is automatic and of the same construcvalve, the speed of the motor shaft 92 in the 50 reverse direction will be the same as the speed previously obtained in a forward direction.

In Fig. 11, there is illustrated a modified form of the means for adjusting the strokes of the pump 39 and motor 3|, more particularly a means for accomplishing the adjustment of these strokes manually. As illustrated in said figure, a piston I22 is located in a cylinder I23" and has a projecting stem 31I which projects through a centrally apertured closure 312 for the right hand end of the cylinder I23. A pair of laterally spaced arms 313 project outwardly from the closure 312 and carry a pivot pin 314 on which an arcuate motion transmitting and direction changing dog 315 is swingably mounted. This dog has one end portion 315 engaging the horizontal stem 3', and another end portion 311 engaging a vertically adjustable stop 318. The stop 318 has a stem 319 extending into a bore 380 in a vertical adjusting screw 38!, the lower end of which is threaded into a bushing 382 secured to a detachable cover 22' of the casing 20. A hand knob 383 is secured to the upper end of the screw 38I iv means of a pin 384, so that the stop 318 may be tion as that-illustrated in Figs. 1 to, 10. Included, however, is a means for retarding the shifting of the wobble plate devices at low speedsso as to retard the acceleration of the output shaft. Referring to Fig. l2,'a control piston I22" is reciprocable in a cylinder I23" which is extended toward the right and has a supplemental piston 386 therein. The piston I22" has an integral extension 389 of reduced diameter, the end of which is attached to the piston 398. The right hand end of the cylinder I23" is supplied with fluid from the low side of the high pressure relief valve 329 through a port 393, a check valve 394, and a port 395 in the closure 393. At low output shaft speeds, the movement of the piston I22" toward the right (Fig. 12) is retarded by means of a restricted outlet orifice 399, the fiow through which may be adjusted by means of a valve device 39I which has an operating stem 392 projectlng up through the casing cover 22". When the pistons move to the right, the check valve 394 is closed. The supplemental piston 385 has a plurality of longitudinal ports 398 therethrough for conducting fluid to the left hand side of said piston and into the portion of the cylinder I23" occupied by the reduced portion 389 of the piston I22". The check valve 394 permits fluid to flow into the cylinder I23" but prevents return flow, with the result that the fluid, at low speeds of the output shaft, must flow out through the restricted orifice 399.

.At higher output shaft speeds, the ,supplemental piston is positioned farther to the right in cylinder I23" than shown in Fig. 12. When the output shaft speeds reach a predetermined high value, the delayed acceleration may not be essential. Accordingly, a supplemental port 391 is provided for exhausting fluid from the cylinder I23". This port serves as a bypass around the restricted orifice 398 whenythe speed of the motor is higher and the supplemental piston 389 has moved toward the right sufilciently to uncover the port 391.

The operation of .the form of invention illustrated in Fig. 12 is similar to that of the form shown in Figs. 1 to 10 with the exception that the reversal of the motor is retarded at low speeds. In the speed range wherein the restricted orifice 399 is effective, the speed of reversal maybe adjusted by means of the valve device 39 I.

I claim as my invention:

1. A fluid transmission having, in combination, a reversible flow pump, a variable speedreversible motor connected to receive the fluid output of said pump, means including a pump control member for reversing the output 0! said pump, means raised and lowered by rotating the screw 38I. [3 including a motor control member for varying the speed of said motor, fluid operated mechanism associated with said pump'and motor control members operable to adjust the motor speed with either direction of fluid flow and means for obtaining any one of a plurality of pre-selected motor speeds comprising adjustable stop devices having parts movable from effective to ineflfective positions with respect to said mechanism, said: movable parts being fluid operated, and means operable selectively to direct fluid to one of said stop devices. 7

2. In acontrol mechanism for adjustable speed fluid motors, in combination, a plurality of adjustable stops, a shifta-ble control element, movably mounted members associated with said stops and control element operable selectively to determine the position of said control element in ac-- cordance with the position of an associated stop, a motor speed control device, and fluid operated means for positioning said device in accordance with the position of the control element.

3. In a fluid transmission having a reversible flow pump and a. variable displacement motor, a pump displacement control element having forward and reverse positions on opposite sides of a neutral position, a motor displacement control element movable from maximum to minimum motor displacement, means for adjusting the pump displacement control element comprising a pair of piston and cylinder devices, racks on the pistons thereof, a pinion interconnecting said racks, means connecting said pump control element to the piston of one of said devices, means for admitting fluid under pressure to the head ends of said cylinders alternatively to move the pump control element to forward or reverse position, and movably mounted means connected to said motor control element shiftable by the tail end of the piston to which fluid is admitted.

4. In a fluid transmission having a variable displacement reversible flow pump and a variable displacement motor, a pump displacement control element having forward and reverse positions on opposite sides of a neutral position, a motor displacement control element movable from maximum to minimum motor displacement, means for adjusting the pump displacement control element comprising a pair of piston and cylinder devices, means interconnecting the pistons thereof for simultaneous operation in opposite directions, means connecting said pump control element to the piston of one of said devices, said last mentioned means operating to move said pump control element to forward or reverse position with movement of said one piston in one or the opposite direction from a neutral position, means for admitting fluid under pressure to the head ends of said cylinders alternatively to move the pump control element to forward or reverse position, movably mounted means connected to said motor control element shiftable by the tail end of the piston to which fluid is admitted, means determining the position to which said selected piston moves said control elements comprising a plurality of adjustable stop devices having parts movable from effective to ineffective positions with respect to said motor element, and means operable to select and effect the movement of said parts individually.

5. A fluid transmission having, in combination, a reversible flow pump, a variable speed motor connected to receive the fluid output of said pump, means for reversing the output of said pump. means including a motor control membe! for varying the speed of said motor. fluid operated means for shifting said motor control member in a direction to increase the motor speed with either direction of fluid flow from said pump, and means for obtaining any one of a plurality of pre-selected motor speeds by adjustments including varying the position of said motor control member comprising a reciprocably mounted plunger associated with said motor control member and having an annular flange thereon, a plurality of cylinders arranged annularly about said plunger adjacent said flange, pistons in said cylinders having side wall notches into which said flange projects, an adjustable stop device for each piston for determining its extent of movement in one direction, and means for selecting and effecting the movement of said pistons into engagement with said stop devices one at a time, the selected piston acting on the plunger in opposition to and overcoming the action of said fluid operated means thereon so that the engagement of the flange on the plunger with one end of the notch in the selected position when abuttin its stop determines the speed of the motor.

6. A fluid transmission having, in combination, a variable speed motor, means to supply fluid under pressure to said motor, means including a.

motor control member for varying the speed of said motor, pressure fluid operated means for urging said motor control member in a direction to increase the motor speed, and means for obtaining any one of a plurality of pre-selected motor speeds comprising a reciprocably mounted plunger associated with said motor control member and having an annular flange thereon, a pluralityof ,cylinders arranged annularly'about said plunger adjacent said flange. pistons in said cylinders each operable to engage the flange and act on said plunger in opposition to and overcoming the action of said fluid operated means thereon, an adjustable stop device for each piston for determining the actuated position thereof, and means for selectin and effecting the movement of said pistons one at a time by pressure fluid into engagement with said plunger and stop devices.

'7. A-fluid transmission having. in combination, a pump, a variable speed motor connected to receive-the fluid output of said pump, means for reversing the output of said pump, means including a motor control member for varying the speed of said motor, fluid operated means urging said motor control member in a direction to increase the motor speed with either direction of fluid flow from said pump, and means for obtaining any one of a plurality of pre-selected motor speeds comprising a reciprocably mounted element associated with said motor control member and having a plurality of cylinders arranged annularly about said element, pistons in said cylinders arranged to engage and act on said element in opposition to and overcoming the action of said fluid operated means thereon when moved in a speed determining direction, an adjustable stop device for each piston for determining its extent of movement in such speed determining direction, and means for selecting and effecting the movement of said pistons into engagement with said stop devices one at a time.

8. In a fluid transmission having a reversible flow pump and a variable displacement motor, a pump control element having forward and reyerse positions, a motor displacement control element movable from maximum to minimum motor displacement, means for adjusting the means connecting said pump control element to the piston of one of said devices, said last mentioned means operating to move said pump control element to forward or reverse position with. movement ofsaid one piston in one or the oppo-- admitting fluid under pressure to the head'ends of said cylinders alternatively to move the pump 1 control element to forward or reverse position, movably mounted means connected to said motor displacement reversible flow pump and a variable displacement motor, a pump displacement control element having forward and reverse positions on opposite sides'of a neutral position, a

motor displacement control element movable,

from maximum to minimum motor displacement,

means for adjusting the pump displacement con-' trol element comprising a pair of parallel piston l and cylinder devices, means interconnecting the site direction from a neutral position, means for 10 control element shiftable by thetail end of the i5 piston to which fluid is admitted; and'means for determining the position to which said selected piston moves said control elements comprising a reciprocably mounted device connected to said to act on said-"device 'inuopposition to and overcoming the'actlon of saidf'forward and reverse pistons thereonQan independently adjustable stop y pistons thereof for'simuitaneous operation in op-' posite directions, means connecting said pump control element to the piston or one of said devices, said last mentioned means operating to move said pump control element to forward or reverse position with movement of said one piston in one or the opposite direction troma neu- =tra1 position, :means for admitting fluid under pressureto the head ends of said cylinders alter- I, natively to move the pump control element to motor control element, a plurality of cylinders,

speed selecting pistons in said cylinders arranged device for eachofsaid speed selecting pistons 5 ior determining the extentrof movement; of said piston in a speed determininpdirection, and means for selecting and efiectingthe movement of said pistons into'engagement with said stop devicesoneatatpnep I 1 x I 9. The combination ofa variable speed motor, means 'foradjusting the speedethereoi comprising a speed control element movable to any one of a plurality'oi positlons, means fordetermirl ing said positions comprising adjustable devices i associatedwith saidv control. element and effective f selectively to' determine the position of i the control element and an adjustable dashpot de- I vice operableto delay the shifting of said conforward or reverse position, and a reciprocably mounted plunger connected to said motor control element and disposed to be abutted and shifted by the tail end of either oi. the pistons or said pairot piston and cylinder devices.- s .4

tions on opposite sides. of a neutral position, a

motor; displacement control element movable from maximum to. minimum motor displacement,

means for adjusting the pumpdisplacement control element comprising apair of parallel piston and cylinder devices, means interconnecting the pistons'thereo'f for simultaneous operation in opposite directions, means connecting said pump trol element from'one position to: another inthe 40 lower rangeof motor speeds, said .dashpot having a bypass portrendering' thedashpot ineffective inithehigherrange of motorspeeds.

10. In a fluid transmission havi g a reversible flow pump and a variable speed' motor, a pump control element having forward stop, and. reverse positions, a motor speed control element movable from maximumto minimum motor speed, means control element to the piston oi! one oi! said devices, said last mentioned means operatingto move said pump control element to forward br reverse position withmovement of said one piston in one or the opposite direction from 'a neutral position, means for admitting fluid under pressure to the head ends of said cylinders alter nativelyto move the pump control element to forward or reverse position or for relieving fluid from said cylinders, a plunger connected to said 'motor control element and disposed to be abutted .and shifted longitudinally by the tail .end of for adjusting the pump control element comprising a pair or pistonand cylinder devices, means interconnecting i the pistonsthereof for simultaneous operation 'in opposite directions, means connecting saidpump' control'element to the piston of one of said devices, said last mentioned means operating *tomov said pump control element to forward or reverse po'sitionwith move-- ment ofsaid one piston" in one orthe opposite direction from a neutral position, means for admittingfiuid under pressure to thehead' ends of said cylinders aIternativelyQ-Ornot 'at allpto move the pump control-element to forward or reverse, or stop position, a movably mounted, member connected to said motor control element shiftable by the tail end of the piston'to which fluid is admitted, manually adjustable means tel-mining the position to which said selected piston moves'said member, adashpotpistonand cylinder device having one-element thereof secured to said member and the other held staeither of the pistonsot said pair of piston and cylinderdevices, and fluid pressure means urging saidplunger inya' direction to restore the pistons of said pair of devices to a neutral position'of the pump control element when the fluid'is re- ,lieved from the head end ofsaid cylinders.

13. In a fluid'transmission having a variable displacement reversible flow pump and a variable displacement motor, a pump displacement control element having forward and reverse positions on opposite sides or a neutral position, a motor displacement control, element movable from maximum to minimum motor displacement,

. means for adjusting the pump displacement contio'nary, means supplying fluid under pressure to said dashpot' cylinder to return the pump control element to its stop position, and a valve controlled port in said dashpot cylinder for delaying-the discharge of fluid Ltlierefrom.

1,1. In a fluid transmission having a-variable (6 trol element comprising a pair of, parallel piston and cylinder devices, means interconnectingmhe pistons thereof for simultaneous operation in oppositedi'rections, means connecting said pump control element to the piston of one'of said devices, said last mentionedmeans operatingto move said pump control element to forward or reverse position with movement of said one piston in one or the opposite direction from a neutral position, means for admitting fluid under pressure to the head ends of saidfcylinders alternativel to move the pump control element to forward or reverse position or for relieving fluid trol element having forward and reverse positions on opposite sides of a neutral position, a motor displacement control element movable from mas-.-

from said cylinders, a plunger and cylinder device with the plunger connected to said motor control element, said plunger being disposed to be abutted and shifted longitudinally by the tail end of either of the pistons of said pair of piston and cylinder devices, and means supp ying fluid under pressure to the end of the cylinder of said plunger and cylinder device constantly urging said plunger in a direction to restore the pistons of said pair of devices to a neutral position of the pump control element when the fluid is relieved from the head ends 01' said cylinders.

14. In a fluid transmission having a variable displacement reversible flow pump and a variable displacement motor, a pump displacement control element having forward and reverse positions on opposite sides of a neutral position, a motor displacement control element movable from maximum to minimum motor displacement, means for adjusting 'the pump displacement control element comprising a pair or parallel piston and cylinder: devices, means interconnecting the pistons thereof for simultaneous operation in opposite directions, means connecting said pump control element to the piston of one of said devices, said last mentioned means operating to move said pump control element to forward or reverse position with movement of said one piston in one or the opposite direction from a neutral position, means for admitting fluid under pressure to head ends of said cylinders alternatively to move the pump control element to forward or reverse position, or for relieving fluid from said cylinders, a plunger connected to said motor control element and disposed to b abutted and shifted longitudinally by the tail end of either of the pistons of said pair of piston and cylinder devices, fluid pressure means constantly urging said plunger in a direction to restore the pistons of said pair of devices to a neutral position of the pump control element when the fluid is relieved from the head ends of said cylinders, and manually adjustable means acting through said plunger to determine the position to which said selected piston moves said control elements.

tons of said pair oi devices to a. neutral posi- '.tion of the pump control element when the fluid is relieved from the head ends of said cylinders, manually adjustable fluid actuated means acting through said plunger to determine the position to which said selected piston moves said control elements, a source of pressure fluid for said last mentioned means diflerent from the source for said plunger and cylinder device, and means for controlling the supply of fluid to said manually adjustable means.

16. In a fluid transmission having a variable displacement reversible flow pump and a variable reverse position'with movement of said one piston in one or the opposite direction from a neutral position, means for admitting fluid under pressure to the head ends of said cylinders alternatively to move the pump control element to forward or reverse position or for relieving fluid from said cylinders, a flrst fluid actuated device urging the pistons of said pair of devices toward neutral position, a second fluid actuated device interconnected with said first fluid actuated device and also operative to urge the pistons of said 1 pair of devices toward neutral position, said first and said second fluid actuated devices being efposition upon relief of fluid from said pair of fective to restore said pair of devices to neutral devices, and means interconnecting said motor control element and one of said first or second fluid actuated devices.

displacement reversible flow pump and a. variable 15. In afluid transmission having a variable,

displacement reversible flow pump and a variable displacement motor, a pump displacement con imum to minimum motor displacement, means 'ment comprising a pair of parallel piston and cylinder devices, means interconnecting, the pisfor adjusting the pump displacement control ele tons thereof for simultaneous operation in opposite directions, means connecting said pump con-,

trol element to the piston of one of said devices, said last mentioned means operating to move said pump control element to forward or reverse position with movement of said one piston in one or the opposite direction from a neutral position, means for admitting fluid under pressure to the head ends of said cylinders alter-' natively'to move the pump control element to forward or reverse position or for relieving fluid from said cylinders, a plunger and cylinder device with the plunger connected to said motor control element, said plunger being disposed to be abutted and shifted longitudinally by the tail end of either of the pistons of said pair of piston and cylinder devices, means supplying fluid under pressure to the end of the cylinder of said plunger and cylinder device constantly urging said plunger in a direction to restore the pis- 17. In a fluid transmission having a variable :displace'ment motor, a pump displacement con- -trol element having forward and reverse posi- -tions on opposite sides of a neutral position, a

tor displacement control element movable from maximum to minimum motor displacement, means for adjusting the pump displacement control element comprising a pair of parallel piston and cylinder devices, means interconnecting the pistons thereof for simultaneous operation in opposite directions, means connecting said pump control element to the piston 01' one of said devices, said last mentioned means operating to move said pump control element to forward or I reverse position with movement of said one" piston in one or the opposite direction from a neutral position, means for admitting fluid under pressure to the head ends of said cylinders alternatively to move the pump control element to forward or reverse position or for relieving fluid from said cylinders, a first fluid actuated device urging the pistons of said pair of devices toward neutral position, a second fluid actuated device interconnected with said first fluid actuated device and also operative to urge the pistons of said pair of devices toward neutral position, said first and said second fluid actuated devices being efl'ective to restore said pair of devices to neutral position upon relief of fluid from said pair of devices, means interconnecting motor displacement control element movable from maximum to minimum motor displacement, means for adjusting the pump displacement control element comprising a pair or par-l allel piston and cylinder devices, means interconnecting the pistons thereof for simultaneous operation in 'opposite directions, means connecting said pump control element to the piston of one of said devices, said last mentioned means operating to move said pump control element to forward or reverse position with movement of said one piston in one or the opposite direction from a neutral position, means for admitting fluid under pressure to the head ends of said cylinders alternatively to move the pump control element to forward or reverse position or for relieving fluid from said cylinders, a first fluid actuated device urging the pistons of said pair of devices toward neutrall position, a second fluid actuated device interconnected :with said first fluid actuated device and also operative to urge the pistons of said pair of devices toward neutral position, said first and said second fluid actuated devices being effective to restore "said pair or devices to neutral position upon relief of fluid from saidpair of devices, means interconnecting said motor control element and one of said first or second fluid actuated devices, manually adjustable means acting on one of said first or second fluid actuated devices to determine the position to which said selected piston moves said control elements, a source of pressure fluid for one of said neutralizing'devices, and a difl'erent source of pressure fluid for the other of d neutralizing devices, said manually adjusts e means and said pair oi piston and cylinder devices.

GUNNAR A. WAELMARK. 

